Loop Gain in High Tonnage Truck Vehicles' Drivers Exposed to Chronic Intermittent High Altitude at the First, Third, and Fifth Day of Nocturnal Sleep

Introduction: The aim of this paper was to measure the loop gain (LG) in central apneas (CA), in workers workers exposed to chronic intermittently high altitude during the first, third and fifth night shift. To asses if the loop gain is attenuated as an indirect surrogate of acclimatization. Material and Methods: This is a secondary crosssectional and descriptive study applied to high tonnage trucks's drivers that work in an open-pit mine located at 4300 m.a.s.l. The drivers alternate ten working days at mine site with ten resting days at home. We used a type III device. The acquisition was taken during the first, third and fifth night while workers were sleeping at mine site. We measured the respiratory cycle and the LG. Inclusion criteria: a) At least ≥3 consecutive CA separated by an interapnea recovery breaths, b) CA Index≥5 and c) More than 50% of events were CA. In order to be included in the analysis, workers must fulfil requirements a, b and c in the first night. We used non-parametric tests for the comparison of continuous values between groups. Results: Seventeen workers, age 41.6±9.7 and all were male. BMI 27.2±1.9 kg/m2, Epworth Sleepiness Scale 4.8±3.5, and living home altitude 1426±1498 m.a.s.l. The values for the first, third and fifth nights were: AHI 33.4±16.8, 21.6±16.3 and 27.9±16.9 (p=0.012), CAI 20.4±13.5, 9.5±9.8, 14.2±14.9 (p=0.022), MediaO2Sat 83.6±2.1, 84.9±2.1, 83.8±3.5 (p=0.019) and LG 1.95±1.88, 2.10±1.20, 3.35±4.23 (p=0.028). Conclusions: Workers had high respiratory index with clear predominance of central events, and profound desaturation. The LG value was over 1 and documented ventilatory instability. This variable showed absence of attenueation of LG and CA Index which could be suggestive that acclimatization was not reached. Funding Statement: Study sponsored by Compania Minera Antamina. Declaration of Interests: All the authors declare no conflict of interest. Ethics Approval Statement: Drivers signed an informed consent. The Comite de Etica de Investigacion from the Universidad Catolica de Santa Maria approved and authorized the study. The study was carried out according to the Declaration of Helsinski.